docstr: Return an iterator over the input layers
docstr_tok: ["Return","an","iterator","over","the","input","layers"]
code: def input_layers(self):
      """Return an iterator over the input layers"""
      for layer_id, in_degree in self.__graph.in_degree():
          if in_degree == 0:
              yield self.__layers_by_id[layer_id]
  
file_path: OMLT/src/omlt/neuralnet/network_definition.py
imports: import networkx
  from omlt.neuralnet.layer import Layer
label_desc: Use image node_id 7 for calling the NetworkDefinition obj's underlying member method code with example usage: obj.input_layers() without return types